One October morning several Little Yellows were visiting the Crucita blooms in my
garden, and I was (vainly) trying to get a good photograph of a Little Yellow in
flight. I began to track a little yellow butterfly moving around the yard. When
I later looked at pictures I realized it was not another Little Yellow but a
Mimosa Yellow. It's never wise to assume you know the species of a butterfly
without checking carefully! It turned out that this female was ovipositing on
shoots of Blackbrush Acacia, Acacia rigidula. The Acacia usually grows as
a bush, but the plants this butterfly visited were all coming up in an area of
that is regularly mown. The eggs I found were all on the tender leaves of new
growth.

I watched a couple of the eggs I found and I collected the caterpillar of this
study as soon as it eclosed. Because of the season and weather, I soon was
unable to locate fresh Acacia leaves for the caterpillar to eat. I offered
Bundleflower (Desmanthus virgatus), because it was more abundant and I
had previously raised a Mimosa Yellow on that plant. Sometimes caterpillars
resist changes in diet, but in this case the caterpillar accepted the new food.

As I often do, I kept the caterpillar in an unheated room, where it experienced
similar temperatures to the outdoors, but was protected from freezing. The
weather was cool, and the caterpillar grew very slowly. It took 46 days to
pupate. It emerged 21 days later, 67 days after the caterpillar eclosed from the
egg. In comparison, the Mimosa Yellow I raised in warmer weather took only
13 days to pupate and emerged 6 days later, only 19 days after the caterpillar
eclosed from the egg. (Both eggs eclosed on the fifth day after being laid.)